Albert Barnes on John 18:22

One of the officers. One of the inferior officers, or those who attended on the court.

With the palm of his hand. This may mean, wave him a blow either with the open hand or with a rod"--the Greek does not determine which. In whatever way it was done, it was a violation of all law and justice. Jesus had showed no disrespect for the office of the high-priest, and if he had, this was not the proper way to punish it. The Syriac reads thus: "Smote the cheek of Jesus." The Vulgate and Arabic: "Gave him a blow."

(2) "with the palm of his hand" or, "with a rod"